In any moderately complex JavaScript program, everything happens inside functions.

Functions are a core, essential part of JavaScript.

What is a function? A function is a block of code, self contained, and we can tell our program to run that code when we need it.

Here’s a function declaration:

function test() {
  // do something
}

The // do something comment is a placeholder for a set of instructions that can be long as much as you want.

When you want to run this function, you “call it” or “invoke it”, like this:

test()

Lessons in this unit: